The airline will continue leasing planes, cabin crew and pilots from other carriers, including Ryanair while a row with its cabin crew over new rosters reaches a critical point.

Ryanair chief executive Michael O'Leary said last night he will lease another four planes to the airline today.

He accused the Aer Lingus cabin crew of "having no sense between their ears by taking industrial action when hundreds of thousands of people are losing their jobs".

"If we can help a union lose a stupid row like that we will be always willing to help," he said.

"They voted for this agreement back in November, and now they won't implement it."

Cabin crew face a tough decision after management threatened them with the sack if they didn't sign documents agreeing to work the new rosters.

It is understood that roughly four members of the cabin crew have already signed up. Letters containing these 'declarations' are being dispatched in phases to another 170 cabin crew who have refused to work the rosters, including 150 who have been struck off the payroll.

They will be invited to disciplinary meetings from tomorrow when management will ask for their decision.

The airline's threat to fire them came after over 4,000 passengers were hit when the airline cancelled over 50 flights last week due to the dispute.

Last night, an Aer Lingus spokesman said "the schedule is planned to operate normally for the coming days" but would not comment on the airline's operational costs due to its leasing arrangements.

Draconian

Aviation sources estimate that aircraft and crew hired at short notice on short-haul flights cost in the region of €40,000 per round trip, with prices around €250,000 for transatlantic flights.

IMPACT, representing the cabin crew, said Aer Lingus is likely to be spending €400,000 as over 10 aircraft were being leased per day. The union said it also faces the cost of refunds to passengers, paying the salaries of its own pilots who are left idle, newspaper adverts about the dispute, and hiring outside staff to conduct disciplinary hearings.

It urged Aer Lingus to "come clean" about its spending as staff, customers and shareholders -- which includes the State with a 25pc stake -- had a right to know how much money was "being wasted".

The roster changes were part of the airline's plan to increase the cabin crews' flying hours to 850 a year.

But the crews claim the changes were draconian and anti-family.

Among the disputed changes was a measure that could result in a crew member's working day being delayed by up to three hours in the event of a disruption, such as staff illness.

The airline claims this is standard international practice, and the previous arrangement was a delay of up to two hours.

IMPACT claims staff cannot take meal breaks on European flights, but the airline denies this and says it provides meals on board flights for them.